1. Field of the Invention
The present invention relates to an antenna structure, and more particularly, to an antenna structure disposing a radiator around another radiator and to make at least one predetermined distance included between the two radiators for matching impedance and for increasing bandwidth of antenna.
2. Description of the Prior Art
With the trend of micro-sized mobile communications products, the location and the space arranged for antennas becomes increasingly limited. Therefore, built-in micro antennas have been developed. Some micro antennas such as chip antennas and planar antennas are commonly used and occupy very small volume.
The planar antenna has the advantages of small size, light weight, ease of manufacturing, low cost, high reliability, and can also be attached to the surface of any object. Therefore, micro-strip antennas and printed antennas are widely used in wireless communication systems.
Due to multimedia applications of present wireless communication products, such as notebook computers, getting more and popular every day, transmissions with a large number of data has become a basic requirement of the wireless communication products. Thus requirements for operations at wide bandwidth get more basic. Therefore, how to improve antenna efficiency, adjust impedance matching, improve radiation patterns, and increase bandwidths of the antennas become important topics in this field.